Day of the Girl is an international observance day declared by the United Nations celebrated each year on October 11th.

Emma Gonzalez

Days after a gunman killed 17 of her peers at her school, Emma Gonzalez used her voice to call national attention to change gun law. Along with her classmates, she held gun control rallies. They also called on officials to prevent future mass shootings from taking place.

In an essay written for Harper’s Bazaar, the 18-year-old spoke about her determination to continue to use her voice until change has occurred.

“If I’m able to communicate one thing, it would be this: It should not be easier to purchase a gun than to obtain a driver’s license. You don’t need an AR-15 to protect yourself when walking home at night. No one does.”

Yara Shahidi

Shahidi is an 18-year-old actress and activist who uses her platform to advocate for girls’ education and voter turnout. Most recently, she sat down with Oprah Winfrey to discuss how she’s turning her activism into action by launching a new initiative called Eighteen x ’18, which will encourage more young people to vote in the upcoming elections.

In the past, she’s worked with Michelle Obama’s Let Girls Learn initiative and with the United Nations to launch a mentorship program called “Yara’s Club,” through the Young Women’s Leadership Network. After completing her gap year, she plans to attend Harvard University as a sociology and African-American studies double major.

Marley Dias

At 13 years old, Dias is the founder of #1000blackgirlbooks. She started in 2015 aiming to donate 1,000 books to her peers that featured black girls.

To date, she has collected more than 10,000 books and spoken at the United State of Women Summit in 2016. This past January, she released her own book, “Marley Dias Gets it Done: And So Can You!” which features opening remarks and praise from Hillary Clinton, Ellen DeGeneres and filmmaker Ava DuVernay.

“I’m working to create a space where it feels easy to include and imagine black girls and make black girls like me the main characters of our lives,” Dias said at Forbes’ Women Summit in New York City last year.

Hannah Price is the 24-year-old British founder of Revolt Sexual Assault. After Hannah was raped as a student, she began using Snapchat to remove the stigma surrounding sexual harassment and assault. Since, she has sparked a national discussion about consent on our campuses and been featured in Elle, the BBC and Huffington Post.

Melati and Isabel Wijsen

These two sisters from Bali are campaigning to get their island home to eliminate plastic bags. At the age of 12 and 10, the sisters were inspired to take action after learning about world leaders and activists in school, including Nelson Mandela and Martin Luther King Jr.

Melati Wijsen says: “We sat on this bench and made a list of problems in Bali. For us, garbage was the biggest thing.”

Jazz Jennings

You probably recognize 16-year-old Jazz Jennings — she is one of the most visible transgender teen girls in the country. Jazz has her own reality TV show, where she provides advice for other trans teens. She is also the first trans spokesperson for Clean & Clear!

Sophie Cruz

Sophie Cruz is a 6-year-old powerhouse fighting for deportation relief. She is a U.S. citizen, but her parents are undocumented immigrants from Mexico. She is an advocate for Deferred Action for Parents of Americans (DAPA) and Deferred Action for Childhood Arrivals (DACA).

Sophie first became known in the movement in August 2015. When the Pope visited Washington D.C., she gave him a letter in order to ask him to protect her parents from deportation.

Nadya Okamoto

Okamoto made headlines when she ran for Cambridge City Council in Massachusetts at only 19. This made her the youngest candidate in the race. She ran on a platform of housing policy and the prevention of gentrification in Cambridge’s low-income neighbourhoods. Although she ultimately lost the election, the Harvard College student remained active in civic engagement.

In 2014, she co-founded PERIOD, a nonprofit organization that distributes sanitary products to people in need, aiming to de-stigmatize menstruation through social and legal change.

She says: “It really is a huge obstacle to global development because it’s holding back more than half our population. We say the menstrual movement is our push to make menstrual hygiene and menstruation a more open topic.”

Scarlett Victoria Clark is Founder and Editor of SMART GIRL TRIBE and a multi-lingual journalist. She has also written for Cosmopolitan, Harper’s Bazaar, Women’s Health. When not writing she enjoys travelling and shopping for (more) heels.